This invention relates to a new and improved apparatus for cubing of thermoplastic material in preparation for use of such materials in further operations.
In the manufacture of thermosetting and thermoplastic materials in the extrusion processes, it is important to provide consistency in the raw material. The extrusion process may receive the raw materials and premix the component elements or receive the raw materials premixed and ready for use such as cubed materials. To many, the latter is preferably as the consistency of initial product for the extruder can be better controlled by manufacturing specialists who blend the PVC resin with plasticizer, stabilizers, and other additives. In preparing the PVC resin for use by such operators the manufacture cubes or dices the thermoplastic materials for bagging and subsequent shipment. It has been the practice to dice cold sheet or milled sheet material from the blenders. Diced PVC is generally of a cube size of 1/8 and 3/32 inch. Most dicing or cubing machines receive the thermoplastic material as it comes from a cooling bath or a spray cooling system. The dicer has a plurality of rotor knives that cooperate with a bed knife. The teeth of the rotor knives are so proportioned in relation to the bed knife that the severing action produces cubes. Variations on this equipment has been tried to speed up the cubing process.
A variation on the above process of dicing has been to use a slitter-chopper arrangement, where the thermoplastic material is cut into multiple strands, afterwhich the strands are fed into a separate machine which are crosscut into cubes by rotor knives against a bed knife as the strands are drawn therebetween. The drawback with a slitter-chopper is that cutting hardened plastics causes a wearing problem on blades and subsequently worn blades result in irregularly shaped cubes. Further, such operation generates dust and noise.
The present invention is directed to a new and improved cuber that operates on a hot strip of thermoplastic material eliminating considerable dust, reducing the energy consumption while increasing the output rate of a slitter-chopper type of apparatus.